Method and apparatus for locating underground cast iron pipe joints
First Claim
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1. A method for locating underground cast iron pipe joints comprising the steps of:
- determining the location and orientation of an underground cast iron pipe;
passing an oscillating electrical current through an electrically driven resonant coil disposed substantially vertically above said underground cast iron pipe, forming an oscillating magnetic field;
inducing an electrical current in each of two resonant sensor coils disposed within said oscillating magnetic field;
measuring a magnetic reluctance between said electrically driven resonant coil and each of said resonant sensor coils, producing an initial magnetic reluctance; and
measuring said magnetic reluctance while moving said coils above and parallel to said cast iron pipe, whereby measured magnetic reluctances substantially different from said initial magnetic reluctance constitutes proximity to a cast iron pipe joint.
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Abstract
An apparatus for locating underground cast iron pipe joints having an electrically driven resonant coil generating an alternating magnetic field and two resonant sensor coils disposed within the alternating magnetic field, each of the resonant sensor coils having an independent magnetic reluctance circuit. A device is provided for comparing electrical currents induced in each of the resonant sensor coils and a device is provided for indicating a relative magnitude of the electrical currents.
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Citations
4 Claims
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1. A method for locating underground cast iron pipe joints comprising the steps of:
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determining the location and orientation of an underground cast iron pipe; passing an oscillating electrical current through an electrically driven resonant coil disposed substantially vertically above said underground cast iron pipe, forming an oscillating magnetic field; inducing an electrical current in each of two resonant sensor coils disposed within said oscillating magnetic field; measuring a magnetic reluctance between said electrically driven resonant coil and each of said resonant sensor coils, producing an initial magnetic reluctance; and measuring said magnetic reluctance while moving said coils above and parallel to said cast iron pipe, whereby measured magnetic reluctances substantially different from said initial magnetic reluctance constitutes proximity to a cast iron pipe joint. - View Dependent Claims (2, 3, 4)
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Specification